Inhibition of Wnt activity improves peri-implantation development of somatic cell nuclear transfer embryos

Somatic cell nuclear transfer (SCNT) can reprogram differentiated somatic cells into totipotency. Although pre-implantation development of SCNT embryos has greatly improved, most SCNT blastocysts are still arrested at the peri-implantation stage, and the underlying mechanism remains elusive. Here, we develop a 3D in vitro culture system for SCNT peri-implantation embryos and discover that persistent Wnt signals block the naive-to-primed pluripotency transition of epiblasts with aberrant H3K27me3 occupancy, which in turn leads to defects in epiblast transformation events and subsequent implantation failure. Strikingly, manipulating Wnt signals can attenuate the pluripotency transition and H3K27me3 deposition defects in epiblasts and achieve up to a 9-fold increase in cloning efficiency. Finally, single-cell RNA-seq analysis reveals that Wnt inhibition markedly enhances the lineage developmental trajectories of SCNT blastocysts during peri-implantation development. Overall, these findings reveal diminished potentials of SCNT blastocysts for lineage specification and validate a critical peri-implantation barrier for SCNT embryos.

Automated summary

Somatic cell nuclear transfer (SCNT) can reprogram differentiated somatic cells into totipotency, but most SCNT blastocysts are arrested at the peri-implantation stage. In this study, a 3D in vitro culture system for SCNT peri-implantation embryos was developed, and it was found that persistent Wnt signals blocked the pluripotency transition of epiblasts, leading to defects in epiblast transformation events and implantation failure. Manipulating Wnt signals improved the cloning efficiency and enhanced the lineage developmental trajectories of SCNT blastocysts during peri-implantation development.